Formal criteria, which are also clinical:
- Occur daily, or every other day, usually for 6-12 weeks [range: 1 week to 1 year], then disappear for at least a month, then recur.
- Each attack lasts 15 minutes to 3 hours. They may strike 1 to 8 times a day.
- The headache is severe, unilateral, felt around the eye or temple.
- At least one other unilateral finding on the same side as the headache (ipsilateral):
- red eye or tearing, eyelid edema, pupil constriction, or ptosis;
- runny nose [nostril] or congestion;
- unilateral forehead or facial sweating;
- restlessness or agitation [this would be bilateral]
Order an MRI, because a disproportionate number of patients with typical signs & symptoms of cluster headache happen to have CNS abnormalities, suggesting possible causality. Inquire about coping mechanisms — suicides have occurred. If headaches mimic clusters, with shorter duration & more frequent bursts, consult a headache specialist.